Japan's wave of personal-data theft from web systems: JPCERT/CC and NICT describe attackers who decompile the published Android app to find internal APIs, drop JSP web shells as .war files on application servers, and run AI penetration-testing platforms against exposed web applications and WSUS servers

JPCERT/CC's alert of 2026-10-08, updated on 2026-10-23, says that around September 2026 Japanese organisations disclosed a run of personal-data leaks through unauthorised access, and singles out an attack type that may be increasing: systems the operator never expected strangers to reach, such as business-intelligence tools and staff-management systems, were hit alongside public apps (JPCERT/CC, 2026-10-23). It does not tie them to one method and groups them in five: per-target scanning for known flaws and exposed configuration and backup files; unauthorised calls to application management APIs; the Metabase SQL injection CVE-2026-72898; .war files carrying a JSP web shell that runs commands passed in query parameters, placed on application servers reachable from the public web server; and, added on 2026-10-23, attempts through AI penetration-testing platforms it names as Cairn, CyberStrikeAI and ARTEX, including against exposed WSUS servers (JPCERT/CC, 2026-10-23).

In the API case the attackers analyse the published smartphone app to find endpoints and keys, then attack internal APIs the app screens cannot reach: changing user rights, creating accounts, toggling a header or sending malformed tokens to compare responses, and blind NoSQL injection to find account data; some use API keys stolen elsewhere (JPCERT/CC, 2026-10-23). NICT calls this an app-to-backend attack: the app need not be vulnerable, and backend authentication, authorisation or input-validation faults leak data (NICT, 2026-10-13). On attack servers JPCERT/CC found Android packages, reverse-engineering tools and a Python script that answers requests with HTTP 302 redirects and appears to have been used to test for server-side request forgery (JPCERT/CC Eyes, 2026-10-21).

No source names an actor. JPCERT/CC says it confirmed that the attackers used AI to scan for known vulnerabilities and attack through APIs (JPCERT/CC Eyes, 2026-10-21), while Macnica could not confirm AI use (Recorded Future, 2026-10-22). API-attack access also arrives through Tor exit nodes and residential proxies (JPCERT/CC, 2026-10-23).

Triage: the app's own User-Agent proves nothing, because JPCERT/CC saw attack requests carrying it; the endpoints called and the sequence (header toggling, malformed tokens, role changes) discriminate, and a TLS fingerprint that matches a generic Python client does not identify the attacker alone (JPCERT/CC, 2026-10-23).